n = int(input())
s = input().strip()

original_count = 0
for i in range(len(s) - 4):
    if s[i] == 'C' and s[i+1] == 'P' and s[i+2] == 'C' and s[i+3] == 'T' and s[i+4] == 'F':
        original_count += 1

candidates = []
for j in range(len(s) - 2):
    if s[j] == 'C' and s[j+1] == 'P' and s[j+2] == 'C':
        if j >= 4:
            if s[j-4] == 'C' and s[j-3] == 'P' and s[j-2] == 'C' and s[j-1] == 'T':
                candidates.append((j, j + 2))

# Sort intervals by their end points
candidates.sort(key=lambda x: x[1])

new_count = 0
prev_end = -1
for start, end in candidates:
    if start > prev_end:
        new_count += 1
        prev_end = end

print(original_count + new_count)